In what ways could irisin mediate the health benefits of exercise?

The initial discovery of irisin and its functions revealed that it induces brown fat–like changes in white fat, including expression of the gene that codes for uncoupling protein (UCP1), which enables brown fat cells to metabolize lipids without producing ATP. As a result, metabolism in the brown fat cells is not inhibited by the buildup of ATP or the lack of ADP, and the brown fat can simply metabolize excess energy and generate heat.

Exercise does more than promote weight loss and toned muscles. It also improves cognition and glucose metabolism. Improving glucose metabolism can help reverse the changes associated with type II diabetes—elevated blood glucose, elevated blood insulin, loss of sensitivity of the pancreas to glucose, and loss of sensitivity of body tissues to insulin. Investigating Life: How Could Irisin Mediate the Benefits of Exercise on Cognition? and Figure 40.15 present experiments showing that irisin is a mediator of benefits of exercise on cognition and glucose metabolism. It seems likely that irisin is a major integrating factor in a large suite of healthful benefits of exercise.

Future directions

The experiments explored in Investigating Life: How Could Irisin Mediate the Benefits of Exercise on Cognition? and Figure 40.15 suggest the interesting possibility that irisin could be developed as a therapeutic that might be useful in treating the national epidemic of obesity and type II diabetes. It might also prove to be beneficial in cognitive declines due to conditions such as stroke and Alzheimer’s disease. Before such treatments can be developed, however, research is needed on such questions as: Are there potential negative side effects of abnormal elevations of irisin? Is there the potential for abuse of irisin, similar to what has been seen with other growth-promoting agents such as growth hormone and testosterone? It would seem that the safest way to benefit from the actions of irisin would be to use the natural approach of regular exercise to promote its normal production and release.